Container for liquid crystal cumulative dosimeter

ABSTRACT

A container for a liquid crystal cumulative dosimeter including a resilient outer body sealed to confine a first liquid crystal composition constituent and a second liquid crystal composition constituent and having at least one transparent section to permit observation of the color of the confined composition, and a barrier contained completely within and physically unattached to the outer body for separating the first constituent from the second constituent, whereby disruption of the barrier allows the first constituent to mix with the second constituent. The barrier is formed either by encapsulating one or both of the constituents or by using air bubbles. Methods of manufacturing the various containers shown and processes of using those containers are also disclosed.

FIELD OF THE INVENTION

This invention relates to a container for packaging a cumulativedosimeter which uses liquid crystal compositions. More particularly, thecontainer separately stores the two reactive liquid crystal compositionconstituents, which form the dosimeter, either by encapsulating one orboth of the constituents or by using air bubbles. To activate thedosimeter, the container allows the constituents to be mixed.

BACKGROUND OF THE INVENTION

The successful storage of perishable packaged foods, pharmaceuticals,and other consumable goods often depends upon the duration andtemperature of storage. The useful life of such goods, their shelf life,can be reduced significantly if storage occurs at temperatures higherthan those recommended. Despite precautions, a number of sources mayinadvertently cause high temperatures: power outages, equipmentbreakdowns, inaccurate thermostats, warm sections in refrigerationunits, unaccountable removal and replacement of the goods, and the like.

Such vagaries prompt the use of expiration dates, which are usuallyconservative estimates of shelf life and which risk premature disposalof useful goods. These uncertainties also risk use of deterioratedgoods. To avoid such risks, devices that indicate whether perishablegoods have accumulated a deleterious amount of thermal exposure proveuseful.

Many devices and materials have been developed to indicate, byreflecting the accumulated time of storage at a predeterminedtemperature, expiration of shelf life. Also known in the art arecumulative dosimeters which reflect the combination of time andtemperature of storage. Cholesteric liquid crystals broadly useful inthe practice of the present invention comprise cholesteric compositionssuch as those described in U.S. Pat. No. 4,066,567, issued to MortimerM. Labes and incorporated herein by reference.

Briefly, these compositions include a cholesteric liquid crystalcompound with one or more of the constituents of the composition adaptedto enter into a chemical reaction. The rate of that reaction isproportional to both the time and temperature of exposure in acumulative manner. The light reflecting properties of the compositionchange in proportion to the degree of completeness of the reaction,usually causing the composition to change color. An extraneous material,such as a solute or diluent, may be added to affect the color of theliquid crystals. Thus, the compositions show a color change exhibiting,for example, that the composition has been exposed to a temperature inthe range of 0°-25° C. for a period of several hours.

The two (or occasionally more) constituents of the compositions whichwill react chemically must be separately stored before use. Separatestorage within the closed system of the cumulative dosimeter containeris necessary to prolong the shelf life of the dosimeter. Consequently,it is also necessary to provide a quick and convenient way to mix theconstituents in the closed system when the dosimeter is to be used.

A number of flexible containers have been devised, in variousconfigurations, to permit separate storage and convenient mixing.Typically, these containers have multiple chambers or compartmentsseparated by rupturable or frangible barriers. U.S. Pat. No. 4,469,452issued to Sharpless et al., for example, discloses a cholesteric liquidcrystal system which has a temperature sensitive membrane locatedbetween the constituents. The membrane prevents mixing until the correcttemperature is reached, after which the reaction starts.

Another reference (U.S. Pat. No. 4,533,640 issued to Shafer) shows anaccumulated thermal exposure device which includes an inner tube filledwith one constituent reactant and an outer tube filled with a secondconstituent reactant. The reactants mix to form an amine and anindicator is: included. One embodiment specifically shows a reactantpackage which has a well of one material and a plug of another separatedby a frangible barrier. Upon application of pressure, the two reactantsare allowed to mix and, if the temperature is correct, to react.

The Sharpless et al. and Shafer references are typical of the prior artcontainers. Each shows an accumulated thermal exposure device withstructural barriers physically attached to the container for separatingtwo components. The device is activated upon removal of the barrier,either when the correct thermal conditions are attained or byapplication of mechanical pressure.

Containers which have a frangible barrier have several drawbacks. Formany containers of this type, the user must mechanically break orrupture the barrier. That action requires great care, because the usermust avoid damage to the container itself. The act of breaking thebarrier without damaging the container is especially difficult when thebarrier is physically attached to the container; the point at which thebarrier breaks must be controlled.

In most, if not all, of the containers using a frangible barrier, thestrength of the barrier and, therefore, the force needed to break it,depend, in substantial part, upon the physical characteristics of thebarrier material. Thus, the physical specifications of the barrier mustbe controlled precisely, a requirement which increases the cost of thecontainer. Moreover, the relatively complex structure of such frangiblebarriers increases the cost of manufacture.

To overcome the shortcomings of existing liquid crystal cumulativedosimeter containers, a new container is provided. An object of thepresent invention is to provide a container which separates thereactants until mixing is desired and which achieves separation with abarrier that is both economical to manufacture and easy to use. Arelated object is to avoid the need for structural barriers which arephysically attached to the container. Another object is to incorporate abarrier which provides good seal integrity, preventing premature mixing,yet minimizes the chances of inadvertent rupture. It is still anotherobject of the present invention to permit activation without damage tothe container itself.

SUMMARY OF THE INVENTION

To achieve these and other objects, and in view of its purposes, thepresent invention provides a container for a liquid crystal cumulativedosimeter which is sealed to contain a cholesteric liquid crystalcomposition with one or more of the constituents of the compositionadapted to enter into a chemical reaction. Because the compositionchanges color in proportion to the degree of completeness of thereaction, the container has at least one transparent section to permitobservation of the color change.

A barrier is contained completely within, but is physically unattachedto, the container. That barrier separates the reactants within thecontainer while the dosimeter is stored. When the user wants to activatethe dosimeter, the barrier is disrupted so that the reactants can mixand, thereby, react.

In a specific embodiment of the invention, the barrier includes aseparating air bubble disposed between the reactants and a ballast airbubble disposed behind one or both of the reactants. To mix thereactants and activate the dosimeter, the user displaces the separatingair bubble, causing it to "join" the ballast air bubble. Suchdisplacement may be accomplished either mechanically or thermally. Aunique advantage of this embodiment is the lack of any structuralbarrier that is ruptured, broken, or permeated inside the container. Thebarrier is opened simply by pushing or kneading the separating airbubble or by cooling sharply one side of the container.

Another aspect of the invention is the novel methods of manufacturingthe above-described container. Briefly, one method includes the steps of(a) providing a resilient sealable enclosure separated into a lower halfand an upper half; (b) placing a predetermined amount of one reactant onthe lower half of the enclosure at a specified position thereon; (c)placing a predetermined amount of the second reactant on the lower halfof the enclosure at a specified distance from the first reactant; (d)covering the lower half of the enclosure with the upper half of theenclosure; and (e) sealing the lower half of the enclosure to the upperhalf of the enclosure so that the specified distance between the firstand second reactants defines the size of the separating air bubblebetween the reactants and the ballast bubble forms behind at least oneof the reactants between the reactant and a wall of the enclosure.

This method can be implemented on a mass production basis, and requireslittle precise machining. In addition, the method allows the amount ofthe reactants used to be precisely controlled. The result is a highlyefficient, economical manufacturing process.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary, but are notrestrictive, of the invention.

BRIEF DESCRIPTION OF THE DRAWING

The invention is best understood from the following detailed descriptionwhen read in connection with the accompanying drawing, in which:

FIG. 1 shows a container in which the outer body of the container has a"dumbbell" configuration and the reactive constituents are separated byone embodiment of the barrier which includes a separating air bubbledisposed between the constituents and a ballast air bubble disposedbehind one of the constituents;

FIG. 2 shows a container in which the outer body of the container has a"dumbbell" configuration and the reactive constituents are separated bythe barrier embodiment of FIG. 1, highlighting that a ballast air bubblemay be disposed behind each of the constituents;

FIG. 3 shows a container in which the outer body of the container has aball-and-plunger configuration and includes a transparent section, areflective section, and a color indicator to facilitate observation andthe reactive constituents are separated by the barrier embodiment ofFIGS. 1 and 2, highlighting the variation possible in location of theair bubbles;

FIG. 4 shows a container in which the outer body of the container has aball-and-plunger configuration and the reactive constituents areseparated by the barrier embodiment of FIGS. 1-3, highlighting thevariation possible in size and position of the ballast air bubble;

FIG. 5 shows a container in which the outer body of the container has atube configuration and the reactive constituents are separated by thebarrier embodiment of FIGS. 1-4;

FIG. 5A illustrates a cross-section of the container shown in FIG. 5taken along line A--A of FIG. 5 and highlights the tack-shaped sectionincluded on the container to affix the container to the goods it willmonitor;

FIG. 6 shows a container in which the outer body of the container is arelatively flat sheet and the reactive constituents are separated by thebarrier embodiment of FIGS. 1-5 and 5A; and

FIG. 7 shows a container in which the outer body is a relatively flatsheet and the reactive constituents are separated by another embodimentof the barrier which includes encapsulation of the separateconstituents.

DETAILED DESCRIPTION OF THE INVENTION 1. The Container of FIGS. 1-7

FIGS. 1-6 and 7 show two barrier embodiments of a container 10, 10A,10B, 10C, 10D, 10E, and 10F for a liquid crystal cumulative dosimeterconstructed in accordance with the present invention. The container 10,10A, 10B, 10C, 10D, 10E, and 10F defines an outer body 12, 12A, 12B,12C, 12D, 12E, and 12F which may have a variety of shapes. Whatever itsshape, the outer body confines a first composition constituent 14, 14A,14B, 14C, 14D, 14E, and 14F and a second composition constituent 16,16A, 16B, 16C, 16D, 16E, and 16F. The first constituent and secondconstituent combine to form a composition based on cholesteric liquidcrystals as described in U.S. Pat. No. 4,066,567. To confine theconstituents and outer body of the container is sealed.

The first constituent and second constituent are adapted to enter into achemical reaction, described more fully in the reference cited above.The rate of that reaction is proportional to the exposure of thecomposition to both time and temperature. The light reflectingproperties of the composition change in proportion to the degree ofcompleteness of the reaction, usually causing the composition to changecolor. An extraneous material, such as a solute or diluent, may be addedto affect the color of the liquid crystals.

In a typical application of the composition, perishable goods may bepackaged with the container of the present invention confining acholesteric liquid crystal including chemical constituents and whichreact at a reasonable rate only at temperatures greater than 25° C. butwhich react at slower rates at temperatures up to 25° C. The cholestericis blended so that its normal color is, for example, red at temperaturesbetween 0° C. and 25° C. with a shift in color brought about by reactionof the constituents to blue, for example. The proposed storagetemperature of the goods is 0° C. or below. At that temperature, thereaction rate of the constituents is substantially zero. Further, theconstituent reaction is controlled by the concentration of theconstituents so that the reaction will be substantially complete withina range of exposure of from 5° C. for 100 to 1,000 hours to 25° C. for 1to 100 hours.

Container 10, 10A, 10B, 10C, 10D, 10E, and 10F may be packaged with thegoods 50 it will monitor for temperature dosage in a number of ways. Thecontainer may be mounted on the surface of the goods at the base 13 ofthe container. The container may also include a section 18 affixed tobase 13 (as shown in FIG. 5A, which is a cross-section taken along theline A--A in FIG. 5). Section 18 is composed of a material capable ofefficient heat transfer and is shaped, for example, like a tack toassure enhanced thermal contact between the container and the goods.Such a section permits the container to better sense the innercumulative temperature exposure of the goods.

In order to facilitate observation of the color of the compositionconfined within the container, the outer body is provided with at leastone transparent section 20 (see FIG. 3). Multiple transparent sectionsmay be provided and, of course, the entire outer body might be made of atransparent material. To further facilitate observation, a reflectivesection 22, typically blackened, is provided on the outer body.Preferably, reflective section 22 is positioned opposite transparentsection 20, as shown in FIG. 3. The entire lower half of the outer body,the half opposite the observer could constitute a reflective section 22.

To help the user evaluate the observed color, a color indicator 24 maybe provided either in or on the outer body. Indicator 24 containsindicia which allow the user to compare the observed color of thecomposition inside the container with typical colors exhibited by thatcomposition and to form a color match. Further indicia inform the userof the cumulative thermal dosage corresponding to the matched color.Placement of transparent section 20, reflective section 22, and colorindicator 24 on the outer body can vary depending on the application forwhich the container is used.

Outer body 12, 12A, 12B, 12C, 12D, 12E, and 12F is made of a resilientmaterial, preferably a thermoplastic material selected for hydrolyticstability and biological inertness. Suitable materials includepolypropylene, polyethylene, polyesters, polyacrylates, certain nylons,and the like. The thickness of outer body 12, 12A, 12B, 12C, 12D, 12Eand 12F is typically about 15 microns. Various shapes for outer body 12,12A, 12B, 12C, 12D, 12E and 12F are possible, some of which aredistinguished in FIGS. 1, 3, 5, and 7. Possible shapes include aball-and-plunger (see FIG. 3), a tube (see FIG. 5), a relatively flatsheet (see FIGS. 6 and 7), and the like. Using the example of FIG. 1, a"dumbbell" configuration is shown. Two circular end sections, each witha diameter of about 5 mm, are connected by a bridge. The bridge is atube about 7 mm long with a diameter of about 1 mm.

Disposed completely within the interior of the outer body is a barrierfor separating the first constituent from the second constituent duringstorage of the container. Although the barrier may contact or touch theinner wall of the outer body, it is not physically attached in any wayto the outer body. Two, alternative embodiments are provided for thebarrier--both of which avoid the known use of structural barriers whichare physically attached to the container and the consequent drawbacks ofsuch containers discussed above.

In the first embodiment, encapsulation is used to enclose one or both ofthe composition constituents, thereby providing a barrier separating theconstituents. The process of encapsulation is well known, as disclosed,for example, in U.S. Pat. No. 3,341,466 issued to Brynko et al. Thethickness of the capsule or microcapsules is chosen to perform twofunctions: it must confine the constituent or constituents withoutleakage during storage and it must break under mechanical application ofmodest pressure when activation of the dosimeter is desired.

An example best explains the meaning of "modest pressure." In a typicalapplication of the present invention, the container will be used tomonitor the cumulative thermal dosage of perishable grocery goods. Itmay be desirable to activate the dosimeter when such goods are labeledin a labelling machine. Accordingly, the relatively modest pressuremechanically applied by the rollers of the labelling machine should besufficient to break the capsule or microcapsules and allow theconstituents to mix and react. Thicknesses on the order of a few micronsare suitable for this purpose.

The first embodiment, encapsulation, is best illustrated in FIG. 7.Microcapsule 40 encapsulates first constituent 14F and microcapsule 42encapsulates second constituent 16F. Microcapsules 40 and 42 may berandomly distributed throughout outer body 12F so that, whenmicrocapsules 40 and 42 are broken, constituents 14F and 16F will, uponrelease, be intermixed and can react.

A second embodiment for the barrier is shown in FIG. 1-6. Disposed inthe interior of outer body 12, 12A, 12B, 12C, 12D, and 12E is an airbubble 30, 30A, 30B, 30C, 30D, and 30E. Formation and placement of theair bubble will be described in connection with the detailed descriptionof the manufacturing method which follows. The barrier created byintimate surface-to-surface contact between the outer body and the airbubble effectively divides the container into two fluid-tight chambers.Each chamber confines a separate constituent, either first constituent14, 14A, 14B, 14C, 14D, and 14E or second constituent 16, 16A, 16B, 16C,16D, and 16E.

Absent mechanical perturbation, the viscosity of the liquid crystalcomposition prevents flow and the constituents will remain separate andunperturbed. It would be essentially impossible to displace the airbubble from between the constituents if there were no other air bubblein the container. If a second, "ballast" air bubble is positioned behindone or both of constituents 14, 16, however, it becomes possible todisplace air bubble 30, 30A, 30B, 30C, 30D, and 30E to "join" ballastair bubble 32, 32A, 32B, 32C, 32D, and 32E. Following such displacement,constituents 14, 14A, 14B, 14C, 14D, and 14E and 16, 16A, 16B, 16C, 16D,and 16E will mix and react. Variations in the design of the container,some of which are shown in FIGS. 1-7, and in the size and position ofair bubbles 30, 30A, 30B, 30C, 30D, and 30E, 32, 32A, 32B, 32C, 32D, and32E are possible without affecting the function of the air bubbles as abarrier.

2. The Method of Manufacturing the Container

The steps of manufacturing a container including a barrier of the typesdiscussed above are outlined below.

Turning first to an encapsulating-type barrier, the manufacturing methodbegins by providing a resilient, sealable (using heat, microwaves, orother common methods of sealing) enclosure which will eventually formouter body 12F. That enclosure is then provided with a predeterminedamount of first constituent 14F. First constituent 14 may be directlyinserted into or on the enclosure. Alternatively, first constituent 14Fmay be encapsulated, with a single capsule enclosing all of constituent14F or numerous microcapsules (as shown in FIG. 7) enclosing portions ofconstituent 14F, and the capsule or microcapsules then inserted into oron the enclosure. For either alternative, a predetermined amount ofsecond constituent 16F is encapsulated and then inserted into or placedon the enclosure. (Again, a single capsule may enclose all ofconstituent 16F or numerous microcapsules (as shown in FIG. 7) mayenclose portions of constituent 16F.) Finally, with both first andsecond constituents 14F, 16F inside the enclosure, the enclosure issealed.

For an air bubble-type barrier, the first manufacturing step alsoinvolves providing a resilient, sealable enclosure which will eventuallyform outer body 12, 12A, 12B, 12C, 12D, and 12E. The enclosure may becontinuously extruded into the interior of an axially-segmented moldwhich is divided into two opposed mold halves. Thus, the enclosure, asprovided, can be separated into a lower half and an upper half. Apredetermined amount of first constituent 14, 14A, 14B, 14C, 14D, and14E is placed on the lower half of the enclosure at a specified positionthereon. A predetermined amount of second constituent 16, 16A, 16B, 16C,16D, and 16E is also placed on the lower half of the enclosure, at aspecified distance from first constituent 14, 14A, 14B, 14C, 14D, and14E.

The two reactive liquid crystal constituents, which combine to form theliquid crystal composition of the cumulative liquid crystal dosimeter,are relatively viscous; they will not flow absent perturbation.Accordingly, placement of the constituents on the lower half of theenclosure will define the size and placement of air bubble 30, 30A, 30B,30C, 30D, and 30E and ballast air bubble 32, 32A, 32B, 32C, 32D, and32E. Although at least one ballast air bubble is required, more may beprovided. A ballast air bubble is placed behind one or both of theconstituents, on the side of the constituent opposite the interfacebetween the constituents. Otherwise, as FIGS. 1-6 show, placement of theair bubbles 30, 30A, 30B, 30C, 30D, and 30E, 32, 32A, 32B, 32C, 32D, and32E may be accomplished in a number of configurations.

Air bubble 30, 30A, 30B, 30C, 30D, and 30E and ballast air bubble 32,32A, 32B, 32C, 32D, and 32E are formed by covering the lower half of theenclosure with its upper half, then sealing the two halves together toform a leak-tight seal. Heat sealing is suitable.

3. The Process of Using the Container

Using the container of the present invention, in the embodiments of thatcontainer disclosed above, one may monitor the accumulated thermalexposure of perishable goods. The first step which must be performed,when using either of the embodiments, is to select a container whichconfines a liquid crystal composition--including a first constituent anda second constituent whose indicator reaction is compatible with theuseful shelf life of the goods to be monitored. It would be senseless toselect a container whose liquid crystal composition reacts between -25°C. and 0° C., for example, if the goods require monitoring between 0° C.and +25° C. The container and goods would be incompatible.

Once the appropriate container is selected, that container must beaffixed to the goods. As discussed above, the container may be affixedto, or mounted on, the surface of the goods. Conventional mountingdevices, such as clips, pins, tapes, adhesives, and the like, aresuitable to affix the container to the goods.

Once the container is affixed to the goods, the indicator reactionbetween the liquid crystal composition constituents must be activated.(It is also possible, however, to accomplish the steps of affixing thecontainer and activating the indicator reaction contemporaneously.) Theprocess of activating that reaction will depend upon which type ofbarrier the container incorporates. Turning first to anencapsulating-type barrier, the capsule (or microcapsules, if bothconstituents 14F and 16F are encapsulated or if multiple microcapsulesare used to encapsulate only second constituent 16F) must be broken sothat the constituents can mix and react. That may be accomplished byapplying mechanical pressure to the container sufficient to break thecapsule or microcapsules but insufficient to harm container 10F.

For the air bubble-type barrier, activation occurs by displacing airbubble 30, 30A, 30B, 30C, 30D, and 30E disposed between firstconstituent 14, 14A, 14B, 14C, 14D, and 14E and second constituent 16,16A, 16B, 16C, 16D, and 16E. Such displacement may be accomplishedmechanically, for example, by applying a roller to container 10, 10A,10B, 10C, 10D, and 10E. It can also be accomplished thermally. Thecontainer is normally stored at room temperature. By sharply cooling oneside of the container, ballast bubble 32, 32A, 32B, 32C, 32D, and 32Ewill compress and air bubble 30, 30A, 30B, 30C, 30D, and 30E willdisplace until it merges with, or joins, the ballast bubble. Absent anintervening air bubble 30, 30A, 30B, 30C, 30D, and 30E constituents 14,14A, 14B, 14C, 14D, and 14E and 16, 16A, 16B, 16C, 16D, 16E will mix andreact.

Following activation, for either the encapsulating or air bubble-typebarrier, the container may be kneaded to create homogeneous mixing ofthe constituents. Alternatively, the indicator reaction may be allowedto proceed at the interface, created by removal of the barrier, betweenthe two constituents. That alternative may prove advantageous if, forexample, a red color emerges at the interface of a blue cholestericsolvent as a function of time and temperature. The color contrastobserved can be striking. Moreover, the observer can judge the extent ofspreading of the color as a criterion for the integral of time andtemperature--in addition to the color itself.

Subsequently, container 10, 10A, 10B, 10C, 10D, 10E, and 10F must bemonitored to observe the indicator reaction. As stated above, theprocess of monitoring is facilitated by transparent section 20,reflective section 22, and color indicator 24 on outer body 12B ofcontainer 10B. Reflective section 22 provides a backdrop highlightingthe color of the liquid crystal composition inside container 10B. Thecolor of the composition is observed through transparent section 20.Then, the observed color is compared to color indicator 24 to evaluatethe thermal dosage accumulated by the goods.

Although the invention is illustrated and described herein as embodiedin a container for a liquid crystal cumulative dosimeter which has anouter body sealed to contain a cholesteric liquid crystal compositionwith one or more of the constituents of the composition adapted to enterinto a chemical reaction; at least one transparent section in the bodyto permit observation of the color change which occurs in proportion tothe degree of completeness of the reaction; and a barrier containedcompletely within, but physically unattached to, the outer body toseparate the reactants within the container while the dosimeter isstored and to allow the reactants to mix upon disruption of the barrier,the invention is nevertheless not intended to be limited to the detailsshown. Rather, various modifications may be made in the details withinthe scope and range of equivalents of the claims and without departingfrom the spirit of the invention.

What is claimed is:
 1. A container for a liquid crystal cumulativedosimeter used to sense the cumulative temperature exposure of aproduct, said dosimeter including a first liquid crystal compositionconstituent and a second liquid crystal composition constituent adaptedwhen mixed to react chemically and to change color in response to saidreaction and in proportion to the cumulative time and temperatureexposure of said constituents, said container comprising:a resilientouter body sealed to confine said first composition constituent and saidsecond composition constituent and having at least one transparentsection to permit observation of the color of the confined compositionformed when said two constituents are allowed to mix; and barrier meanscontained completely within and physically unattached to said outer bodyfor separating said first constituent from said second constituent, saidbarrier means including an air bubble disposed between said first andsaid second constituents and a ballast air bubble disposed behind one ofsaid first or said second constituents, whereby disruption of saidbarrier means allows said first constituent to mix with said secondconstituent.
 2. A container as claimed in claim 1 wherein said containerhas a reflective section to facilitate observation of the color of theconfined composition.
 3. A container as claimed in claim 2 wherein saidreflective section of said container is disposed opposite saidtransparent section of said container.
 4. A container as claimed inclaim 1 wherein said product has a surface and said container has ashape adapted to be affixed to said surface of said product for sensingthe cumulative exposure thereof.
 5. A container as claimed in claim 4wherein said container further includes means for affixing saidcontainer to said surface of said product.
 6. A container as claimed inclaim 1 wherein said container further includes a base and a sectionaffixed to said base, said section composed of a material capable ofefficient heat transfer and adapted to assure enhanced thermal contactbetween said container and a product to which said container isattached.
 7. A container as claimed in claim 1 wherein said containerfurther includes a color indicator for comparison to the color of saidcomposition contained in said container to determine the cumulativethermal dosage sensed thereby.
 8. A container as claimed in claim 1wherein said outer body of said container is formed of a thermoplasticmaterial selected from the group consisting of polypropylene,polyethylene, polyesters, polyacrylates, and nylons.
 9. A container asclaimed in claim 1 wherein said barrier means further includes a secondballast air bubble disposed behind the outer of said first or saidsecond constituents.
 10. A container as claimed in claim 1 wherein saidproduct has a surface and said container has a shape adapted to beaffixed to said surface of said product for sensing the cumulativeexposure thereof.
 11. A container as claimed in claim 10 wherein saidcontainer further includes means for affixing said container to saidsurface of said product.
 12. A container for a liquid crystal cumulativedosimeter used to sense the cumulative temperature exposure of aproduct, said dosimeter including a first liquid crystal compositionconstituent and a second liquid crystal composition constituent adaptedwhen mixed to react chemically and to change color in response to saidreaction and in proportion to the cumulative time and temperatureexposure of said constituents, said container comprising:a resilientouter body sealed to confine said first composition constituent and saidsecond composition constituent and having at least one transparentsection to permit observation of the color of the confined compositionformed when said two constituents are allowed to mix; and barrier meanscontained completely within and physically unattached to said outer bodyfor separating said first constituent from said second constituent, saidbarrier means including at least one capsule for enclosing one of saidfirst or said second constituents, whereby the application of modestmechanical pressure breaks said capsule and allows said firstconstituent to mix with said second constituent.
 13. A container asclaimed in claim 12 wherein said container has a reflective section tofacilitate observation of the color of the confined composition.
 14. Acontainer as claimed in claim 13 wherein said reflective section of saidcontainer is disposed opposite said transparent section of saidcontainer.
 15. A container as claimed in claim 12 wherein said containerfurther includes a base and a section affixed to said base, said sectioncomposed of a material capable of efficient heat transfer and adapted toassure enhanced thermal contact between said container and a product towhich said container is attached.
 16. A container as claimed in claim 12wherein said container further includes a color indicator for comparisonto the color of said composition contained in said container todetermine the cumulative thermal dosage sensed thereby.
 17. A containeras claimed in claim 12 wherein said outer body of said container isformed of a thermoplastic material selected from the group consisting ofpolypropylene, polyethylene, polyesters, polyacrylates, and nylons. 18.A container as claimed in claim 12 wherein said barrier means furtherincludes at least one second capsule for enclosing the other of saidfirst or said second constituents.